SharePoint Online, I have created a content type for text files and it is available as "New Text Document" in document library new document menu. When I click on new text document I get following error. I have content types for word, excel and power point documents and all are working fine. Text files are not supported?
SharePoint opens document using SharePoint.OpenDocuments.ActiveX by design. Text Documents are opened by notepad.exe, and for security reasons only Office Applications are allowed to use the ActiveX control. You can still upload and download text document to and from the library, but not from SharePoint. You need to edit text documents outside of SharePoint and upload them to SharePoint once you’re finished.
Reference: Text document could not be created